Radar sensors are used in motor vehicles with increasing frequency. Such radar sensors are used, for example, in vehicle assistance systems in order to reliably detect oncoming traffic, or approaching vehicles, for example, at greater distances, and to be able to determine as precisely as possible their position and speed, or relative speed and azimuth angle. Radar sensors are also used to monitor the closer proximity of the motor vehicle.
Radar sensors are currently used that generate an outgoing signal, which is emitted, and receive and process the outgoing signal reflected by objects as an incoming signal. The outgoing signal is a series of individual signals having a predetermined time period and frequency, also referred to as a “burst,” which vary in frequency from one individual signal to the next individual signal.
The radar sensors are operated, for example, with the so-called LFMSK transmission method (Linear Frequency Modulated Shift Keying). With this method, three nested individual signals A, B, C are emitted. For a time period of ca. 25 μs (burst) in each case, a constant frequency is emitted thereby, which is then modified linearly for each of the three individual signals. An increasing frequency is referred to as an up-chirp, and a decreasing frequency is referred to as a down-chirp. In addition to the up-chirp and the down-chirp, a mono-frequency individual signal, the so-called Doppler-chirp, is used.
Due to the limitation of the permissible frequency range for automotive applications, and the simultaneous increased used of such radar sensors, the probability increases that vehicles equipped with radar sensors will interfere with each other. In the event of such an interference, the receiver-side radar sensor (victim) also receives, in addition to its own outgoing signal, the outgoing signal of another radar sensor (disrupter).
This results in erroneous evaluations, when the outgoing signal of the disrupter is regarded as the reflected outgoing signal of its own radar sensor.